1. Field of the Invention
The present invention relates to novel compounds useful for synthesizing antibacterially active piperazine benzoxazine derivatives. More particularly, the present invention is concerned with (+)2-benzoyl-3-(silyloxyprop-2(S)-yl)amino acrylate derivatives and a preparing method thereof.
2. Description of the Conventional Art
Intermediates for synthesis of (-)piperazine benzoxazine derivatives and preparing methods thereof are disclosed in German Patent No. 3,543,513; Chemical Abstract 107, 154342c (1987); L. A. Mitscher et al., J. Med. Chem., 30, 2283 (1987)).
German Patent No. 3,543,513 (1987) and Chemical Abstract 107, 154342c (1987) relate to compounds of the type ##STR2## and a preparing method thereof. However, the preparation method comprising reacting ethyl ethoxymagnesium malonate with 2,3,4,5-tetrafluorobenzoyl chloride to give ethyl(2,3,4,5-tetrafluorobenzoyl)acetate, reacting the ethyl(2,3,4,5-tetrafluorobenzoyl)acetate with triethyl orthoformate and acetic anhydride, and substituting with 2-amino-1-propanol, is complicated and the product yield is relatively low.